Transition Metal Catalysed Chain-Growth Polymerization of 1,4-Diethynylbenzene into Microporous Cross-linked Poly(phenylacetylene)s: the Effect of Reaction Conditions
Abstract
Chain-growth polymerization of 1,4-diethynylbenzene into conjugated crosslinked polyacetylene-type poly(1,4-diethynylbenzene)s (PDEBs) is reported. While metathesis catalysts (WCl6/Ph4Sn, MoCl5/Ph4Sn, Mo Schrock carbene) fail in this polymerization, insertion Rh catalysts ([Rh(nbd)acac], [Rh(nbd)Cl](2)) provide microporous PDEBs in high yields.
The Brunauer-Emmett-Teller (BET) surface, S-BET, of PDEBs prepared with [Rh(nbd)acac] increases, in dependence on the polymerization solvent, in the order: THF << pentane < benzene < methanol < CH2Cl2. S-BET further increases with both increasing monomer concentration and increasing polymerization temperature and reaction time, reaching a highest value of 1469 m(2) g(-1).
In addition to micropores, PDEBs contain mesopores. The mesopore volume and average mesopore diameter increase with the time and the temperature of the polymerization up to 2.52 cm(3) g(-1) and 22 nm (72 h, 75 degrees C).
The post-polymerization thermal treatment of PDEB (280 degrees C) results in formation of new crosslinks and modification of PDEB texture and sorption behavior manifested mainly by enhancement of H-2 adsorption capacity up to 4.55 mmol g(-1) (77 K, 750 Torr).